Nutrient load reduction is a well-recognized requirement for aquatic ecosystem restoration. However, decision making is difficult due to challenges related to uncertainty and the interaction between decision makers and modelers, including (a) the quantitative relationship between risks arising from different aspects and the fact that cost is not usually revealed and (b) the fact that decision makers are not significantly involved in the modeling process. In this study, an interactive optimal-decision procedure with risk-cost tradeoff is proposed to overcome these limitations. It consists of chance-constrained programming (CCP) models, risk scenario analysis using the Taguchi method, risk-cost tradeoff and feedback for model adaption. A hybrid intelligent algorithm (HIA) integrating Monte Carlo simulation, artificial neural networks, and an augmented Lagrangian genetic algorithm was developed and applied to solve the CCP model. The proposed decision procedure and HIA are illustrated through a case study of uncertainty-based optimal nutrient load reduction in the Lake Qionghai Watershed, China. The CCP model has four constraints associated with risk levels indicating the possibility of constraint violation. Sixteen risk scenarios were designed with the Taguchi method to recognize the interactions between multiple constraint risks and total cost. The results were analyzed using the signal-to-noise ratio, analysis of variance, and multivariate regression. The model results demonstrate how cost is affected by risk for the four constraints and show that the proposed approach can provide effective support for decision making on risk-cost tradeoffs. (C) 2014 Elsevier Ltd. All rights reserved.
Two gas-phase formaldehyde (HCHO) measurement techniques, a modified commercial wet-chemical instrument based on Hantzsch fluorimetry and a custom-built instrument based on fiber laser-induced fluorescence (FILIF), were deployed at the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) to compare the instruments' performances under a range of conditions. Thermolysis of para-HCHO and ozonolysis of 1-butene were used as HCHO sources, allowing for calculations of theoretical HCHO mixing ratios. Calculated HCHO mixing ratios are compared to measurements, and the two measurements are also compared. Experiments were repeated under dry and humid conditions (RH < 2% and RH > 60 %) to investigate the possibility of a water artifact in the FILIF measurements. The ozonolysis of 1-butene also allowed for the investigation of an ozone artifact seen in some Hantzsch measurements in previous intercomparisons. Results show that under all conditions the two techniques are well correlated (R-2 >= 0.997), and linear regression statistics show measurements agree with within stated uncertainty (15% FILIF + 5% Hantzsch). No water or ozone artifacts are identified. While a slight curvature is observed in some Hantzsch vs. FILIF regressions, the potential for variable instrument sensitivity cannot be attributed to a single instrument at this time. Measurements at low concentrations highlight the need for a secondary method for testing the purity of air used in instrument zeroing and the need for further FILIF White cell outgassing experiments
Highly pi-conjugated perylenediimide (PDI) oligomers are promising low band gap organic materials for various applications in optoelectronics. In this work, individual fluorescence dynamics of ethynylene- and butadiynylene-bridged dimeric and trimeric PDIs (PEP, PBP, and PEPEP) were monitored and analyzed by single-molecule fluorescence spectroscopy to gain information on the degree of extension of pi-conjugation through the acetylene bridge in PDI multichromophores. The simultaneous measurements of fluorescence intensity, lifetime, and spectrum indicate a sequential decrease in pi-conjugation upon photobleaching of PDI monomer units. Furthermore, Huang-Rhys (HR) factors, S, are obtained to evaluate the degree of electronic coupling in view of pi-conjugation and overall rigidity between the PDI units in PDI oligomers at the single-molecule level. In addition, butadiynylene-bridged dimeric PDI (PBP) reveals conformational heterogeneity due to the long butadiynylene linker. These results suggest a new way to control the photophysical properties of the PDI multichromophoric system by expansion of pi-conjugation and modification with different linker groups.[GRAPHICS]
A self-terminating gate recess wet etching technique with thermal oxidation of the AlGaN/GaN layer followed by etching in potassium hydroxide (KOH) solution was recently proposed by the present authors for normally-off AlGaN/GaN metal-oxide semiconductor field effect transistors (MOSFETs). In this present reported work, the oxidation process inside the AlGaN/GaN heterostructure involved in this technique was analysed using several material characterisation methods. The measurement results show that the concentration and depth of the O element distribution increase with increased thermal oxidation temperature. It is worth noting that after 650 degrees C oxidation almost no O element could be found in the GaN layer and the O element mainly locates in the AlGaN layer with an obvious correlation between the distribution of Al and O elements, where the Al(Ga)-oxide was detected by X-ray photoelectron spectroscopy, which could be etched by 70 degrees C KOH. Thus, self-terminating wet etching on the AlGaN/GaN material is achieved.
In this letter, we investigated the behaviors of surface-and buffer-induced current collapse in AlGaN/GaN high-electron mobility transistors (HEMTs) using a soft-switched pulsed I-V measurement with different quiescent bias points. It is found that the surface-and buffer-related current collapse have different relationship with the gate and drain biases (V-GS0, V-DS0) during quiescent bias stress. The surface-induced current collapse in devices without passivation monotonically increases with the negative V-GS0, suggesting that an electron injection to the surface from gate leakage is the dominant mechanism and the Si3N4 passivation could effectively eliminate such current collapse. The buffer-induced current collapse in devices with intentionally carbon-doped buffer layer exhibits a different relationship with V-GS0 after surface passivation. The buffer-related current collapse shows a bell-shaped behavior with V-GS0, suggesting that a hot electron trapping in the buffer is the dominant mechanism. The soft-switched pulsed I-V measurement provides an effective method to distinguish between the surface-and buffer-related current collapse in group III-nitride HEMTs.
A three-stage heavy ion acceleration scheme for generation of high-energy quasimonoenergetic heavy ion beams is investigated using two-dimensional particle-in-cell simulation and analytical modeling. The scheme is based on the interaction of an intense linearly polarized laser pulse with a compound two-layer target (a front heavy ion layer + a second light ion layer). We identify that, under appropriate conditions, the heavy ions preaccelerated by a two-stage acceleration process in the front layer can be injected into the light ion shock wave in the second layer for a further third-stage acceleration. These injected heavy ions are not influenced by the screening effect from the light ions, and an isolated high-energy heavy ion beam with relatively low-energy spread is thus formed. Two-dimensional particle-in-cell simulations show that approximately 100MeV/u quasimonoenergetic Fe24+ beams can be obtained by linearly polarized laser pulses at intensities of 1.1x1021W/cm2.
It has been claimed for more than a century that atmospheric new particle formation is primarily influenced by the presence of sulfuric acid. However, the activation process of sulfuric acid related clusters into detectable particles is still an unresolved topic. In this study we focus on the PARADE campaign measurements conducted during August/September 2011 at Mt Kleiner Feldberg in central Germany. During this campaign a set of radicals, organic and inorganic compounds and oxidants and aerosol properties were measured or calculated. We compared a range of organic and inorganic nucleation theories, evaluating their ability to simulate measured particle formation rates at 3 nm in diameter (J(3)) for a variety of different conditions. Nucleation mechanisms involving only sulfuric acid tentatively captured the observed noon-time daily maximum in J(3), but displayed an increasing difference to J(3) measurements during the rest of the diurnal cycle. Including large organic radicals, i.e. organic peroxy radicals (RO2) deriving from monoterpenes and their oxidation products, in the nucleation mechanism improved the correlation between observed and simulated J(3). This supports a recently proposed empirical relationship for new particle formation that has been used in global models. However, the best match between theory and measurements for the site of interest was found for an activation process based on large organic peroxy radicals and stabilised Criegee intermediates (sCI). This novel laboratory-derived algorithm simulated the daily pattern and intensity of J(3) observed in the ambient data. In this algorithm organic derived radicals are involved in activation and growth and link the formation rate of smallest aerosol particles with OH during daytime and NO3 during night-time. Because the RO2 lifetime is controlled by HO2 and NO we conclude that peroxy radicals and NO seem to play an important role for ambient radical chemistry not only with respect to oxidation capacity but also for the activation process of new particle formation. This is supposed to have significant impact of atmospheric radical species on aerosol chemistry and should be taken into account when studying the impact of new particles in climate feedback cycles.
BACKGROUND: Numerous genetic risk factors of ischemic stroke (IS) have been reported from both candidate gene and genome-wide strategies with inconsistent results. The objective of this study was to confirm the relationship between 10 previously identified single-nucleotide polymorphisms (SNPs) and IS in the Chinese population. METHODS: A family-based study was conducted in a rural area of Beijing, with a total of 227 IS families with 622 participants recruited. Both linkage and association analyses were performed, with all the sibling pairs derived from the 227 families analyzed using the sib-pair test of model-free linkage to assess linkage between SNPs and IS, with association analyses including a family-based association test (FBAT) and generalized estimating equations (GEE). RESULTS: Nonparametric linkage analysis revealed that the rs1800796 polymorphism in the interleukin-6 (IL-6) gene is significantly linked to the small arterial occlusion (SAO) subtype (p=0.022), while the rs7193343 polymorphism in the ZFHX3 gene is linked to IS (p=0.002) under the dominant model. Significant allelic associations were identified between the G allele of rs1800796 and IS (p=0.042) and the SAO subtype (p=0.025) in the FBAT. The GEE method revealed that the G allele of rs1800796 increased IS risk by 1.55-fold (95% 95% confidence interval [CI]: 1.01, 2.37; p=0.043) and 2.43-fold (95% CI: 1.32, 4.45; p=0.004) in the SAO subtype in the dominant model, which correlated with the significant associations detected in the FBAT. CONCLUSIONS: In this study, we confirmed that the SNP of rs1800796 in the IL-6 gene is related to IS and the SAO subtype using different statistical approaches. These findings could contribute to identifying individuals with a high IS risk.